Large scale, multi-story buildings are typically constructed of steel and concrete. Floors in such buildings may be composite floor systems assembled by spanning wide flange beams with spaced-apart steel joists and installing typically corrugated metal decking over the joists. The decking forms a lateral surface onto which a cementitious slab can be placed and cured. Generally, the underside of the beams or lower chords of the joists form the framework from which ceilings may be supported. The composite floor construction is typically achieved by using welded shear studs, or partial extension of the joist upper chord, extending above the form or metal deck into the cementitious slab. Flooring system designs must also be mindful of fire safety, acoustics, and vibration considerations.
Such composite floor systems have been designed in the past to address one or more of these issues individually. These prior designs have included some systems that integrated the joist and deck assembly with the cementitious slab to provide a composite floor system. This integral structure was assembled by providing self-drilling studs with a threaded portion to be in threaded engagement with the deck and underlying joists. A length of each stud extended above the metal decking and was encased in the cementitious slab, and resisted and transmitted horizontal shear forces which develop between the cementitious slab and the supporting joist structure. See U.S. Pat. No. 5,605,423. These composite floor systems were an improvement, but still had drawbacks in that the floor systems were time consuming and difficult to install. There was still a need for a composite floor system that was rapidly and safely installed with fewer building errors to provide a floor system with improved erectability and economy for the same or greater load bearing capacity.
Disclosed is an improved composite joist floor system comprising a first support structure, a second support structure, a plurality of joists spaced apart and extending from the first support structure to the second support structure, decking supported by the plurality of joists, and a plurality of stand-off fasteners adapted to be fastened through the decking to the plurality of joists, each stand-off fastener of carbon steel comprising a lower portion and an upper portion where the lower portion has a clamping part capable of clamping the decking to the joist, the lower portion having a threaded portion adjacent the clamping part with a through hardness of between HRB 70 and HRC 40 and having the lower portion of the fastener with a failure torque to thread-forming torque of at least 3.0 and a drive torque at least 20% less than a thread-forming torque, a thread-forming portion adjacent the threaded portion of at least HRC 50 hardness adapted to enable the fastener to form threads in an upper chord of a joist, and a fluted lead portion adjacent the thread-forming portion of at least HRC 50 hardness with a nominal diameter between 80 and 95% of major diameter of the threaded portion adapted to form a fastener opening in an upper chord of a joist, and the upper portion of the stand-off fasteners have a through hardness of between HRB 70 and HRC 40 and when installed, at least a portion of the upper portion of each stand-off fastener extends significantly above the decking. The composite floor system is completed by providing a cementitious slab supported by the decking and encapsulating the upper portion of each stand-off fastener extending above the decking. The threaded portion of the fastener may extend to within 1.5 of a thread pitch of the clamping part of the fastener.
The threaded portion of each stand-off fastener may meet a specification selected from the group consisting of ASTM A307, ASTM A325, ASTM A354, and ASTM A490 specification or a specification selected from the group consisting of SAE J429 Grade 2, SAE J429 Grade 5, and SAE J429 Grade 8.
The stand-off fasteners of the composite joist floor system may have a drive torque no more than 50% of a thread-forming torque. In any case, the lower drive torque enables the fasteners to be rapidly installed through the deck and into a joist upper chord with low consumption by battery powered tools with a worker in a short time, with the thread forming torque in forming the threads in the deck and joist following drilling of the fastener opening and the seating torque desired for the fastener being the controlling torques in positioning the fastener. This low power consumption and labor saving installation is enabled by the nominal diameter fluted lead portion of the fastener adapted to form a fastener opening in an upper chord of a joist between 80 and 95% of major diameter of the threaded portion or between 80 and 98% of major diameter of the threaded portion. Additionally, the failure torque of the fastener is more than three (3) times the thread-forming torque and may be more than four (4) times the thread-forming torque so that the prospect of the fastener failing and lessening the load capability of the composite floor system is avoided. The thread-forming torque of each stand-off fastener may be no more than 100 inch-pounds.
The failure torque is substantially more than the seating torque of the fastener. The threaded portion of each stand-off fastener may have a seating torque of at least 80 inch-pounds, or between 80 and 450 inch-pounds to provide the proper seating torque, depending on the size of the stand-off fastener and type and properties of the decking, joist and other support material into which the stand-off fasteners are threaded. The threaded portion of each stand-off fastener may also have a thread angle of less than 50°, or may have a thread angle between 45 and 60° Alternately or in addition, the threaded portion may include back-tapered threads for ease of installation. The back-taper of the threaded portion may be between 0.0005 and 0.0025 inch per inch of length or between 0.001 and 0.003 inch per inch of length.
The thread-forming portion of each stand-off fastener may be between 3 and 7 thread pitches in length to provide desired thread-forming torque. To further improve the speed of assembly and improve the load carrying capacity of the composite floor the shape of the thread-forming portion of the stand-off fastener may be selected from the group consisting of bilobular, trilobular, quadlobular and pentalobular. Of these the quadlobular shape has been found to date to give the best performance in thread forming. In any event, these lobar shapes of the thread-forming portion of the fastener control the thread-forming torque and drive torque to facilitate assembly of the composite floor system and reduce failures in installation of the stand-off fasteners and improve the load carrying capacity of the assembled composite floor system.
In addition, the fluted lead portion of the stand-off fastener may have a milled point to reduce the failure rate of the stand-off fastener. Pinch point may be provided on the fluted lead portion of the stand-off fastener, but we have found the fasteners made with a milled point are more reliable and result in less failures of the stand-off fastener, reducing assembly time and cost and producing an assembled composite floor assembly with greater load capacity.
Another aspect of the present composite floor system is the threaded portion of the fastener has a through hardness of between HRB 70 and HRC 40, while the fluted lead portion and most if not all of the thread-forming portion has a hardness of at least HRC 50. Such through hardness on the threaded portion of the fastener enables the composite floor system to support higher loads as the fastener interacts with the cementitious slab and avoids cracking and fracturing of the fastener. The threaded portion of each stand-off fastener may be of at least HRC 33 through hardness and up to five threads adjacent the thread-forming portion may be hardened to at least HRC 50 hardness. To further facilitate assembly of the composite floor system, the fluted lead portion may be of at least HRC 54 hardness or of at least HRC 50 induction hardness. The upper portion of the stand-off fasteners have a through hardness of between HRB 70 and HRC 40 to provide ductility in the upper portion of the fastener to reduce cracking in the fasteners in operation in a cementitious slab of the composite joist floor system.
In addition, the clamping portion of the lower portion of each stand-off fastener of composite joist floor system may comprise a fastener drive head positioned to be used in installing the stand-off fastener and the upper portion of the stand-off fastener is sized to permit the stand-off fastener to be installed into the decking. A SEMS anchor or stake anchor may be positioned on the upper portion of the stand-off fastener sized to permit the stand-off fastener to be installed into the decking and a joist upper chord and the SEMS anchor or stake anchor engage in the cementitious slab on installing of the fastener and placement of the cementitious slab. Optionally, the stand-off fastener may include threads adjacent the end of upper portion of the fastener configured to couple to a reinforcing member such as rebar or some other member that will effectively extend the length of the stand-off fastener. These embodiments further improve the composite floor system by further reducing failures in positioning the fasteners, and at the same time reducing the time to assemble the floor system. Stand-off fasteners utilizing the SEMS anchor or stake anchor also are easy to produce and improve the load carrying capacity of the composite floor system at the same time.
The decking may comprise corrugated steel decking defining altering peaks and valleys, where the stand-off fasteners are installed in the valleys of the corrugated steel decking, and where adjacent stand-off fasteners along a joist are separated by at least one valley of the corrugated steel decking. Alternatively or in addition, the decking may comprise corrugated steel decking defining altering peaks and valleys, and at least two adjacent stand-off fasteners are located in the same valley of the corrugated steel decking.
Also disclosed is a wall panel system comprising a metal base adapted to support placement of a cementitious material, a plurality of stand-off fasteners for fastening at spaced locations along the base, each stand-off fastener of carbon steel comprising a lower portion and an upper portion where the lower portion has a threaded portion, a thread-forming portion adjacent the threaded portion adapted to enable the fastener to form threads in the base, and a fluted lead portion adjacent the thread-forming portion with a nominal diameter between 70 and 95% of major diameter of the threaded portion adapted to form a fastener opening in the base, and where, when installed, at least a portion of the upper portion of each stand-off fastener extends significantly above the base; and a cementitious slab formed on the base and encapsulating the upper portion of each stand-off fastener extending above the base to form a desired wall surface of the panel system.
The lower portion of the fasteners of wall panel system may have a threaded portion with a through hardness of between HRB 70 and HRC 40 and the lower portion of the fastener has failure torque to thread-forming torque of at least 3.0 and a drive torque at least 20% less than a thread-forming torque. The stand-off fastener may have a drive torque no more than 50% of a thread-forming torque. In addition, the thread-forming portion adjacent the threaded portion of a wall panel system has at least HRC 50 hardness adapted to enable the fastener to form threads in the base, and a fluted lead portion adjacent the thread-forming portion of at least HRC 50 hardness. The threaded portion of each stand-off fastener may be of at least HRC 33 through hardness and up to five threads adjacent the thread-forming portion may be hardened to at least HRC 50 hardness. The fluted lead portion may have at least HRC 54 hardness. The upper portion of the stand-off fasteners have a through hardness of between HRB 70 and HRC 40 to provide ductility in the upper portion of the fastener to reduce cracking in the fasteners in operation in a cementitious slab of the wall panel system.
These wall panel systems are typically assembled with the lower portion of the stand-off fasteners drilled and threaded into the metal base. The base may comprise corrugated metal decking assembled and fastened to wall studs. In any case, temporary or permanent side walls may surround the metal base and support the concrete during placing and curing of the cementitious slab. The wall may extend above the upper portion of the stand-off fasteners so the surface of the cementitious slab provides a desired wall surface for the panel system without upper portions of the fasteners showing through. In this way a composite wall panel can be assembled that can be lifted into place. The wall panel system has the metal base, cementitious slab and stand-off fasteners as an integral wall system that can provide a desired wall surface where cracking of the cementitious slab is inhibited if not eliminated. The wall panel system may be used either as an inside wall system or an outside wall system as explained in more detail below with reference to the drawings.
To facilitate assembly and avoid assembly defects, the clamping portion of the lower portion of each stand-off fastener may comprise a fastener drive head positioned to be used in installing the stand-off fastener, with the upper portion of the stand-off fastener sized to permit the stand-off fastener to be installed into the base. An SEMS anchor or stake anchor may be positioned on the upper portion of the stand-off fastener sized to permit the stand-off fastener to be fastened into the base, with the SEMS anchor or stake anchor (threaded or unthreaded) engaging in the cementitious slab on installing of the fastener and placement of the cementitious slab. These embodiments provide for easier installation, while improving the quality and integrity of composite wall panel system assembled.
Alternatively, a fastener drive head may be positioned on the upper portion of each stand-off fastener adapted to be used in fastening the stand-off fastener to the base and to engage in the cementitious slab on installing of the fastener and placement of the cementitious slab. In this embodiment, SEMS anchor is part of the lower portion of each stand-off fastener and adapted to engage the base and the cementitious slab on placement of the cementitious slab.
To facilitate assembly of the wall panels, the thread-forming portion of each stand-off fastener has a shape selected from the group consisting of bilobular, trilobular, quadlobular and pentalobular.
For the wall panel systems, the threaded portion of each stand-off fastener may meet a specification selected from the group consisting of ASTM A307, ASTM A325, ASTM A354, and ASTM A490 specification or a specification selected from the group consisting of SAE J429 Grade 2, SAE J429 Grade 5, and SAE J429 Grade 8.
As with the composite floor systems, the fluted lead portion of the stand-off fastener may have a milled point to reduce the failure rate of the stand-off fastener. Pinch point may be provided on the fluted lead portion of the stand-off fastener, but as previously observed, we have found the fasteners made with a milled point are more reliable and result in less failures of the stand-off fastener, reducing assembly time and cost and producing an assembled composite floor assembly with greater load capacity